A bearing arrangement of this type is described in the abstract of the publication of Japanese patent application JP58017328 A. It is customary to arrange the measuring sleeves between the bearing and the support for the bearing. The support is as a rule a housing or that part of a housing, in which or on which the machine element is arranged. However, the support can also be a separate bearing block or the like, by way of which the machine element is mounted. The machine element is, for example, an axle or shaft which is mounted by means of the bearing arrangement rotatably with respect to the support. The respective measuring sleeve in bearing arrangements according to the prior art is arranged radially between the outer ring of the bearing and the seat in the housing. The measuring sleeve is provided, for example, with strain gauges which react to elastic deformation of the measuring sleeve. The dimensional changes result from reaction supportive forces and displacements which are caused by the machine element which is loaded with forces/moments in the bearing.
The accuracy of the measured results in arrangements of this type of the prior art is dependent on many factors and therefore insufficient in some circumstances. The measured results are dependent, for example, on the rigidity of the support and on the installation tolerances, on temperature influences and on coefficients of thermal expansion of the materials of the housing and of the bearing ring.
Strain elements or the like are calibrated to a predefined initial state before operation of the bearing arrangement. The measuring device in bearing arrangements of the prior art is realized in transmissions on the bearing arrangement which has already been completely mounted in the housing, since, for example, the prestress of a press fit or the prestresses by means of screw connections on the measuring sleeve have to be taken into consideration during the calibration. The prestress which is reflected in deformations in the bearing is dependent on the above-mentioned tolerances and fluctuates from the installation in one transmission to the next installation in another transmission, with the result that the measuring devices have to be adapted individually for each transmission. The time for mounting the transmission is increased. Bearing arrangements having measuring devices of the generic type have therefore not established themselves so far in transmissions of mass production for cost reasons.
In a prestressed bearing arrangement, in which the coefficient of thermal expansion of the material of the measuring sleeve differs from the coefficient of thermal expansion of the bearing ring or the housing, changes in the operating temperature can lead to misleading measured results. It is possible, for example, that the prestress falls or increases on account of this difference. It is intended to measure only the stresses from the loadings on the bearing. Since, however, the prestress in the bearing arrangement can change at the same time as the loadings on the bearing, it cannot be determined clearly which influences have led to the measured results.
The installation space for the corresponding measuring elements or a corresponding sensor system is limited. For the measuring elements, a region which is correspondingly free of loadings has to be provided between the bearing ring and the housing, since the sensitive measuring elements, such as strain gauges, cannot be loaded by pressure, for example.
The outer ring and the measuring sleeve tend to migrate on the circumferential side, with the result that, for example, cable connections to the measuring elements can be subjected to a tensile load and destroyed over time as a result of the migration. The routing of the cables to and from the sensor system is difficult, since the cable leadthroughs in transmissions, for example, have to be sealed.